1. Field of the Invention
This invention relates to an apparatus for making a nonwoven web comprising a carding drum, a continuously moving, air-permeable collecting surface member for collecting fibers which fly in an entraining air stream from the carding drum, a suction box, which is connected to the collecting surface member on that side thereof which is opposite to the carding drum, and a suction duct between the carding drum and the collecting surface.
2. Description of the Prior Art
To make a nonwoven web from a lap, it is known from U.S. Pat. No. 3,641,628 to disintegrate the lap by means of a carding drum into individual fibers and to blow off the covering formed by the individual fibers under the action of centrifugal force by means of an entraining air stream which is tangential to the carding drum so that the nonwoven web is formed in that the individual fibers are deposited on a collecting surface member, which is disposed below the carding drum and is continuously moved and through which the air stream is sucked. Said apparatuses have the disadvantage that the individual fibers cannot be deposited on the collecting surface as uniformly as desired, particularly if the fibers are supplied at a high rate, because the length of the flight path for the fibers between the region in which they are detached from the carding drum and the region in which they impinge on the collecting surface member necessarily depends on the diameter of the carding drum so that there is a considerable risk of formation of lumps, particularly if the working width is large. This is due to the fact that large working widths require carding drums which are large in diameter so that the fibers fly over larger distances.
To ensure a uniform detaching of the fibers from the carding drum and an undisturbed deposition of the fibers on the collecting surface member, it has been proposed to provide between the carding drum and the collection surface a plurality of suction ducts, which are consecutively arranged in the direction of rotation of the carding drum and extend substantially radially with respect to the carding drum so that the individual fibers into which the lap has been disintegrated by the carding drum can be divided into a plurality of partial streams of fibers, which are consecutively deposited on the collecting surface member. Because fibers at a correspondingly lower rate are conveyed in each of said partial streams of fibers, the tendency of a formation of lumps is greatly reduced. But a higher expenditure is involved in the detaching of the fibers from the carding drum in separate layers for the formation of a plurality of partial streams of fibers.